Research in focus

Fraunhofer Institute for Building Physics

A feast for research

Does it taste as good as it smells? "A feast for research" has recently become the motto in the flight test facility at the Fraunhofer Institute for Building Physics IBP in Holzkirchen. In-flight menus for Germany’s Lufthansa AG have already been tested on six occasions in the worldwide unique flight test facility. After relatively basic initial experiments in previous years, this time it was a question of adding the "finishing touches" with special essences and oils. Why? Because it is still true that everything tastes different in the air. "In the air, food and drink tastes as it does when we have a cold," says aroma chemist Dr. Andrea Burdack-Freitag, explaining the effects of reduced pressure in the aircraft cabin on our taste experience.

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A great deal of work goes into the preparation for the taste tests in the low-pressure chamber at Fraunhofer IBP. "One day of testing in the flight test facility requires at least 14 days of preparation," reveals Burdack-Freitag. Everything must be organized – from the correct structure of the test procedure and preparation of the questionnaires for the test subjects, to the delivery and fault-free use of the ovens on board the aircraft, right through to the technical preparation for the flight. On the day of the tests itself, approximately ten Fraunhofer IBP employees are then tasked with ensuring that everything runs smoothly. For example, there are at least three »pilots« in the cockpit – which in fact is situated outside the low-pressure chamber – who use the control station to ensure that there is no turbulence during the flight. And within the flight test facility itself, besides the chefs from LSG Sky Chefs, some six IBP staff are busy handing out questionnaires, giving safety instructions, serving food and drink to the test subjects and overseeing the series of tests to ensure that they are performed in the correct order. 

On this occasion – the sixth time so far that the flight test facility has been in operation for Lufthansa AG and its subsidiary LSG Sky Chefs – menus were tested which had already previously been adjudged on the ground to be "suitable for flight". The results of previous experiments from this comprehensive series of tests had shown that salt is perceived to be between 20 and 30 percent less intense and sugar 15 to 20 percent less intense. The perception of fruity aromas and acids is by contrast more stable. This means for example that the flavor of Asian dishes, which have a very intense aroma anyway, remains stable at low pressure. Milder dishes such as fish or poultry, on the other hand, require much more seasoning with salt and herbs. The chefs at LSG Sky Chefs have implemented these results in the dishes which they have created and this time served three versions of each menu: one with neutral flavors and two with more seasoning. A range of different seasoning oils, such as coffee oil, and tomato essences were used as natural flavor intensifiers. In the right amounts, seasoning oils lend support to the aroma of dishes, while tomato essences can help to provide a harmonious taste experience.

"Nevertheless," explains Fraunhofer scientist Burdack-Freitag, "the results of tests such as these are very subjective." It isn’t possible to satisfy everyone’s tastes, she says, and the results of the statistical evaluation must therefore ultimately be adapted to the so-called mainstream when creating new versions of menus. Lufthansa AG is currently implementing the results of this comprehensive series of tests in the preparation of its in-flight catering.

Background information:
There are various reasons why people’s perceptions of smells and tastes are different in the air than on the ground. On the one hand, the reduced pressure in the aircraft affects the human body: oxygen saturation in the blood is reduced, thus also reducing the effectiveness of the olfactory and taste receptors. Meanwhile, flying also affects psychological perception. "If the environment is different, perception also changes," explains Dr. Andrea Burdack-Freitag. In the unfamiliar environment of the aircraft cabin, people are more exposed to basic stimuli and less likely to notice details. This pushes up stimulus thresholds, with the result that a stronger stimulus is required to trigger a response.

The flight test facility at Fraunhofer IBP consists of a low-pressure chamber with a 16-meter-long section of an Airbus A310-200 suspended inside it. The interior furnishings largely correspond to those of a standard aircraft, giving the test subjects an authentic impression, while allowing environmental parameters to be altered: air pressure, cabin external wall temperature, relative humidity, noise level, vibration, light, air circulation and much more. This means that besides taste testing the flight test facility at Fraunhofer IBP allows a wide range of other scientific experiments to be performed, for example on cabin conditions.
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More information about experiments in the flight test facility and about research in the field of aviation can be found here:

Individual climate control in aircraft
EU-funded research project "iSPACE" promises higher thermal comfort for passengers

A question of "ecolonomy"
The Fraunhofer Institute for Building Physics IBP is presenting its innovative work at the world’s largest air show in Le Bourget, France
 

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